x86/entry/64: Simplify reg restore code in the standard IRET paths (e872045b) · Commits · 戴 / test

The old code restored all the registers with movq instead of pop. In theory, this was done because some CPUs have higher movq throughput, but any gain there would be tiny and is almost certainly outweighed by the higher text size. This saves 96 bytes of text. Signed-off-by:

Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bpetkov@suse.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/ad82520a207ccd851b04ba613f4f752b33ac05f7.1509609304.git.luto@kernel.org Signed-off-by:

Ingo Molnar <mingo@kernel.org>

arch/x86/entry/calling.h

+21 −0

Original line number	Diff line number	Diff line
		@@ -151,6 +151,27 @@ For 32-bit we have the following conventions - kernel is built with
		UNWIND_HINT_REGS offset=\offset extra=0
		.endm

		.macro POP_EXTRA_REGS
		popq %r15
		popq %r14
		popq %r13
		popq %r12
		popq %rbp
		popq %rbx
		.endm

		.macro POP_C_REGS
		popq %r11
		popq %r10
		popq %r9
		popq %r8
		popq %rax
		popq %rcx
		popq %rdx
		popq %rsi
		popq %rdi
		.endm

		.macro RESTORE_C_REGS_HELPER rstor_rax=1, rstor_rcx=1, rstor_r11=1, rstor_r8910=1, rstor_rdx=1
		.if \rstor_r11
		movq 6*8(%rsp), %r11

arch/x86/entry/entry_64.S

+6 −6

Original line number	Diff line number	Diff line
		@@ -618,9 +618,9 @@ GLOBAL(swapgs_restore_regs_and_return_to_usermode)
		1:
		#endif
		SWAPGS
		RESTORE_EXTRA_REGS
		RESTORE_C_REGS
		REMOVE_PT_GPREGS_FROM_STACK 8
		POP_EXTRA_REGS
		POP_C_REGS
		addq $8, %rsp /* skip regs->orig_ax */
		INTERRUPT_RETURN


		@@ -650,9 +650,9 @@ GLOBAL(restore_regs_and_return_to_kernel)
		ud2
		1:
		#endif
		RESTORE_EXTRA_REGS
		RESTORE_C_REGS
		REMOVE_PT_GPREGS_FROM_STACK 8
		POP_EXTRA_REGS
		POP_C_REGS
		addq $8, %rsp /* skip regs->orig_ax */
		INTERRUPT_RETURN

		ENTRY(native_iret)

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